The threat of a major explosion at a Southern California aerospace facility is "off the table" after firefighters performed an all-night operation Sunday to test the pressure inside a cracked tank in Orange County, officials told CBS News, as more than 50,000 people remain under evacuation orders.

The threat of a major explosion at a Southern California aerospace facility is "off the table" after firefighters performed an all-night operation Sunday to test the pressure inside a cracked tank in Orange County, officials told CBS News, as more than 50,000 people remain under evacuation orders.

In an incident update posted on X, Orange County Fire Authority Interim Chief TJ McGovern said that the threat of a BLEVE, or Boiling Liquid Expanding Vapor Explosion, has been eliminated at GKN Aerospace in Garden Grove.

"We are happy to report that the threat of a BLEVE is now off the table," said OCFA Interim Chief TJ McGovern. "That threat has been eliminated."

McGovern said Sunday that a BLEVE was the potential worst-case scenario.

In an earlier post, McGovern said that crews discovered a crack in the tank on Saturday night, which could be due to a pressure release. On Monday, OCFA Incident Commander and Division Chief Craig Covey confirmed the existence of a crack, which led to a pressure release. The tank's internal temperature has decreased from 100 degrees to 93.

"That is incredibly positive news as we turn the corner on this incident," Covey said.

An OCFA spokesperson on Monday qualified an earlier update provided by officials, noting that although the threat of a massive explosion has been ruled out at GKN Aerospace in Garden Grove, the potential exists that a smaller blast could occur at the site of the chemical incident. 

While the risk of a worst-case scenario BLEVE has been "eliminated," according to McGovern, an agency spokesperson said the remaining flammable material in the tank still has the potential to burn and ignite.

Evacuation orders will remain in place for an undisclosed amount of time.

The threat of toxic chemicals leaking out of the tank is still possible, according to OCFA PIO Nick Garton.

"It's still a potential," he told CBS LA. "We're trying to confirm that there's still a liquid form of this chemical that could potentially leak out."

Garton made it clear that there is no active leak, but more cracks at the bottom of the tank could potentially form. As pressure continues to lower, however, so do the chances of those cracks forming.

The Orange County Fire Authority told CBS LA on Sunday evening that multiple cracks existed in the tank. But in a post to X later that night, the agency qualified those reports, saying: "To clarify, there is one known crack on the tank. There is also peeling of weather stripping on the exterior, but this is not an additional crack."

OCFA Public Information Officer Wayhowe Huang later clarified that the constant hose stream on the tank was causing the peeling away of the weather stripping, which could have caused confusion about the number of cracks in the tank. 

As of Saturday night, firefighters said that the internal temperature of the tank was over 100 degrees, more than double the "happy place" for the substance.

A White House official told CBS News on Monday that the Trump administration "is engaged and monitoring the situation in Garden Grove," noting that federal resources were assisting with the response.

"The U.S. EPA has integrated with the local Unified Command composed of state and local agencies, and has enabled air monitoring at 20 locations around the area," the White House official said. "FEMA has deployed a Liaison Officer to coordinate with officials and has also deployed a team to the State Emergency Operation Center to support incident contingency planning. FEMA has also activated the Interagency Modeling and Atmospheric Assessment Center to provide plume modeling of airborne hazards, informing incident leadership and contingency planning." 

The news came after California Gov. Gavin Newsom said he requested that President Trump issue an Emergency Declaration. The action would activate FEMA to direct federal assistance at the scene and allow federal funding to flow in.

"California doesn't wait for disaster to unfold, we act early to protect lives and communities," Newsom said. "Working together with our local and federal partners, we're strengthening our ability to respond quickly and effectively in Garden Grove and across the surrounding communities and ensuring that first responders have the resources they need to keep people safe."

The action differs from a Presidential Major Disaster Declaration in that it comes as a preemptive measure, rather than as a response to a disaster that's already caused damage. It's not yet clear if Mr. Trump will grant the request.

After Newsom's request, Democratic U.S. Sens. Alex Padilla and Adam Schiff, and Orange County Rep. Derek Tran, co-signed a letter to Trump urging him to approve the state's request for a Federal Emergency Declaration.

"The severity of this disaster requires additional coordination and federal support," said part of the letter. "The safety, security, and well-being of evacuated residents and the surrounding communities remain my absolute highest priority."

On Sunday, Newsom said that more than 785 state and first responders had been deployed to Orange County to assist local authorities and hazardous material experts, as well as support the communities that were evacuated by the incident. The deployment comes a day after he proclaimed a state of emergency in Orange County on Saturday.

Covey said on Saturday that the temperature inside the tank was rising at a rate of about one degree per hour. That was contrary to the agency's thinking on Friday, just hours after the leak caused the first evacuation orders on Thursday night.

When speaking to reporters on Sunday, California State Sen. Tom Umberg, who represents the area, said the temperature read 100 degrees during Saturday night's operation, which is as high as the reading goes. He called the potential release of pressure "a good thing."

"That may avoid the two concerns that we all had," he said. "One was an explosion, the other was a leak of liquid material vaporizing into a toxic fume, a toxic plume."

OCFA officials confirmed with CBS LA that they were sending a crew in to assess why there were cracks in the tank, hopeful that it was because pressure was being released. They also said it's possible that vapor buildup caused the cracking, which would eventually lead to a rupture or explosion.

Read more here: CBS News Los Angeles